1. Field of the Invention
The present general inventive concept relates to a servo track writing method and a servo track write system of a hard disk drive (HDD) using the servo track writing method, and more particularly, to a servo track writing method of removing process time delay factors of a series of rework processes of writing servo patterns on a disk in order to shorten a process time of the rework processes and improving productivity of a HDD, and a servo track write system of the HDD using the servo track write method.
2. Description of the Related Art
Hard disk drives (HDDs) record data on and/or reproduce data from disks using heads to contribute to operations of computer systems.
Bits per inch (BPI) and tracks per inch (TPI) of disks in present HDDs have been increased. BPI indicates densities in rotation directions of the disks, and the TPI indicates densities in radius directions of the disks. The size of disks in such HDDs have been decreased, while capacities and densities of disks have been increased. Therefore, more sophisticated mechanisms are required for reading and writing information to the disks of the HDD.
A HDD requires servo information to control a position of a head on a magnetic disk so as to read data from and/or write data on the magnetic disk in a desired position.
Writing of such servo information on a disk refers to servo track write.
A servo track write is greatly classified into Conventional Servo Track Write (CSTW) and Offline Servo Track Write (OLSTW).
The CSTW is to permanently write servo information on a disk using a predetermined servo writer after a HDD is assembled.
In the CSTW, after a head disk assembly (HDA) is assembled, the servo information is written. Thus, the servo information is written based on a spindle motor. Accordingly, rotation tracks, which are made by a head along the servo information, are hardly different from substantial rotation tracks of the disk.
However, since the servo information is written after the HDA is assembled, a large amount of time is required to write the servo information. In particular, the number of tracks is increased with an increase in recording density of a HDD. Therefore, the time required for performing a process of writing the servo information on the disk is gradually increased in contradistinction of the whole process.
Differently from the CSTW, the OLSTW is to load a disk, on which servo information has been already written, into a HDD.
In the OLSTW, several disks are stacked, and then servo patterns necessary for servo information are pre-written on the stacked disks. If the OLSTW is used, servo patterns are generally written only on a side of a disk, i.e., a first surface of the disk which is a lower surface of the disk.
For reference, data and servo patterns may be written on both sides of a disk. Those of ordinary skill in the art generally refer to a head, which is disposed on a first surface to read and write information, as #0 head and to a head, which is disposed on a second surface to read and write information, as #1 head. Here, the first surface is a lower surface of the disk, and the second surface is an upper surface of the disk. Hereinafter, for convenience, #0 head and #1 head will be referred to as first and second heads, respectively.
Disks, having first surfaces only on which servo patterns have been written using OLSTW as described above, are assembled with a HDD and then experience a reference check (R/C) process.
Qualities of the servo patterns are first checked through the R/C process. Here, if the qualities of the servo patterns are not good or defective, servo patterns are re-written by an additional servo writer in rework processes.
If the servo patterns are to be re-written in the rework processes due to the defective states of the qualities of the servo patterns, pre-written servo patterns must be erased.
A work of erasing the servo patterns is generally performed by a magnet eraser.
However, since the magnet eraser has a structure in which an erase head is disposed only on an upper surface of a disk on which a second head is positioned, the magnet eraser substantially erase only servo patterns written on the upper surface of the disk.
Accordingly, if servo patterns of an object to be erased are written on a lower surface of a disk on which a first head is disposed, the magnet eraser may not be used.
In this case, existing servo patterns are erased and new servo patterns are written using a servo writer which adopts Push Pin Type Servo Track Write (PPTSTW). The PPTSTW is to erase servo patterns, which are pre-written in all tracks of a disk, one by one and write new servo patterns.
As described above, the servo writer using the PPTSTW erases the servo patterns written in the all tracks of the disk, moving each one of the tracks of the disk and then re-writes servo patterns. Therefore, a process time required for erasing the pre-written servo patterns one by one is unnecessarily increased, and thus rework processes are delayed. As a result, a process time of the rework processes is increased, and manufacturing cost of a HDD is increased.
In particular, rework processes are increased in the case of a HDD having high TPI. This is a factor of lowering productivity of the HDD.